Diagnostic and control method for a vehicle system

ABSTRACT

Methods and systems are provided for controlling and diagnosing a mechanical vehicle component. In one example, a method may include determining a vehicle speed and a plurality of clutch position settings at a diagnostic controller, and identifying unauthorized conditions based on these determinations. Further, the diagnostic controller may trigger an active fault state of the mechanical vehicle component in order to avoid unauthorized conditions that may lead to unwanted or unanticipated changes in vehicle motion.

TECHNICAL FIELD

The present description relates generally to control and diagnosticstrategies in a vehicle system. More particularly, the presentdescription relates to techniques for fault monitoring in a drivelinesystem.

BACKGROUND AND SUMMARY

Different sets of vehicle driveline conditions may lead to unintendedbehaviors. The unintended behaviors may include unwanted changes invehicle acceleration and other undesirable kinematic behavior. Forinstance, a number of conditions can cause erroneous clutch settingsthat may lead to unwanted vehicle braking or movement in an unintendeddirection. In an attempt to avoid these unwanted behaviors, previousvehicle control and diagnostic systems have guarded against unintendedbehaviors by verifying actual settings against requested settings. Whenthe mismatch in the settings is too large, actions are taken todiscontinue or altogether avoid the unintended behaviors.

U.S. Pat. No. 7,980,981 B2 to Kawaguchi et al. discloses a vehiclesystem including an automatic transmission that includes a plurality ofclutches and brakes to change the gear ratio of the transmission. Thesystem determines whether or not at least one or more of the clutches isbrought into unintended engagement. Said determination is carried outanalyzing vehicle deceleration and an intended gear ratio and an actualgear ratio.

U.S. Pat. No. 8,548,712 B2 to Oesterreicher et al. discloses a vehiclesystem and method for fault monitoring of drive operations, particularlyfor preventing vehicle acceleration if a set-point drive torque deviatessignificantly from an accelerator pedal input. The method includescomparing a calculated vehicle acceleration against the expected vehicleacceleration.

The inventors have recognized several drawbacks with the systems andmethods disclosed by Kawaguchi and Oesterreicher, as well as otherdiagnostic systems. For instance, fault detection strategies which relyon comparison of actual vs. intended gear ratio are processing intensivestrategies that may lead to the incorrect identification of a fault, incertain situations. This superfluous fault detection may restrictvehicle performance and lead to unnecessary servicing of the vehicle, insome cases. Further, Kawaguchi's diagnostic logic is provided in asingle engine control unit responsible for component control operationsand fault detection in the vehicle system. This may involve complexprocessing strategies that are not always effective or reliable, due tothe fault misdiagnoses, described above. Additionally, using a singlecontroller for both diagnostic and control operations may prove to beinflexible and inefficient with regard to altering or updating routinesof either operation. Further, other prior fault detection strategieshave involved complex systems that use a comparatively large number ofinputs and guard against a large number of unwanted settings such assoftware faults, hydraulic faults, etc. As such, previous diagnosticstrategies may demand a large amount of processing resources toimplement, and therefore may decrease the system's processingefficiency. Therefore, the inventors have recognized a need for a moreeffective and efficient diagnostic system for fault detection.

To overcome at least a portion of the aforementioned drawbacks, a methodfor operation of a vehicle system is provided. In one example, themethod includes determining, at a diagnostic controller or processingunit, a vehicle speed from a vehicle speed sensor and a position of aplurality of clutches in a transmission of the vehicle system. Themethod further includes identifying an unauthorized clutch positionbased on the clutch positions and the vehicle speed. The method evenfurther includes, in response to identification of the unauthorizedclutch position, operating the plurality of clutches in a fault state.In one example, the fault state or mode may be realized by removingeither all or most of the torque applied at vehicle wheels by removingthe closing force of the clutches, bringing them into an opened state.Therefore, the system can effectively and efficiently identify a clutchfault and operate the clutches to reduce the chance of unwanted vehicledeceleration. Consequently, the operator's experience is enhanced.Further, by executing the diagnostics and driveline control on separatecontrollers or processing units increases the system's adaptability.

In one example, the unauthorized clutch position may be identified bycomparing the vehicle speed and the clutch position against a lookuptruth table. Rows of the lookup truth table are populated with lower andupper speed thresholds that correspond to a plurality of unauthorizedclutch position settings. In this way, the clutches may be diagnosedusing an efficient and reliable routine that has higher diagnosticconfidence than strategies which compare actual and intended clutchsettings, thus guarding against both undesired clutch conditions whichmay lead to unwanted changes in vehicle kinematic performance (e.g.,unintended vehicle deceleration) and unwarranted triggering of the faultstate that may hamper vehicle performance.

In another example, the method may make use of a fault tolerant time asan entry condition for operating the component in the fault state. Inthis example, the fault state of the vehicle component is implementedonce the duration of the fault exceeds a threshold fault tolerant time.The fault tolerant time may be a fixed or dynamic value, and as such maybe selected to activate the fault state or mode in order to achieve ahigher fault diagnostic accuracy.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic depiction of a vehicle system with a controller.

FIG. 2 is a flow chart depicting an example control and diagnosticprocess of a vehicle system.

FIG. 3 is a flow chart depicting another example control and diagnosticprocess of a vehicle system.

FIG. 4 is a lookup truth table depicting unauthorized operatingconditions, for use with the control and diagnostic process shown inFIG. 3.

FIG. 5 is a graphical representation of unauthorized vehicle operatingranges.

FIGS. 6-7 show timing diagrams depicting use-case control and faultdiagnostic strategies.

DETAILED DESCRIPTION

The following description relates to a driveline component controlstrategies and fault diagnostics in a vehicle system. The system usesefficient logic for confident and independent fault diagnosis to reducethe likelihood of undesired driveline and more generally vehiclebehaviors. The system uses independent controllers, or processing units,to implement nominal driveline control strategies and diagnostic (e.g.,fault detection) strategies. As such, diagnostic routines may beexecuted independently from nominal control strategies and is notinfluenced by the nominal control strategies. Thus, a diagnosticcontroller determines a fault condition of a driveline component andtriggers a fault state to operate the driveline component in a faultmode, overriding the nominal control settings of a driveline controller.The separation of control and diagnostic logic allows for independentalteration of control and fault applications, providing increased systemadaptability and diagnostic reliability. This adaptability may result inefficient integration of fault diagnostics into an existing controlarchitecture, as well as the ability to independently update orotherwise alter diagnostic and/or control architecture in a wide varietyof driveline platforms.

To achieve the diagnostic efficiency gains, the diagnostic routinecompares actual component settings to thresholds that are anticipated tocause unwanted kinematic vehicle behavior (e.g., unintendedacceleration/deceleration or vehicle movement in an unintendeddirection). The thresholds may be stored in a lookup truth table andcorrespond to values which have a high likelihood of causing theunwanted kinematic behavior. This comparison may disregard intendedsettings to achieve greater accuracy in the fault diagnosis, using lowercomputational intensive calculations than previous strategies. Thediagnostic system may further determine if a fault duration exceeds afault tolerance time that may be correlated to the component's reactiontime. By using the fault duration in this manner, the diagnosticaccuracy may be further increased. Mapping the diagnostic thresholds tovalues that have a greater chance of causing unwanted vehicle movementto trigger a fault, as opposed to triggering a fault whenever componentsettings deviate from intended values, drives down the likelihood ofincorrect fault generation. Situations where the vehicle issuperfluously placed in the fault state, which may impact vehicleperformance, may be avoided.

FIG. 1 illustrates a high-level vehicle system architecture that usesdifferent controllers to execute a nominal control module and adiagnostic module. This configuration allows for diagnostic routines tobe executed independently from, and in tandem with, nominal controlstrategies, resulting in a highly reliable setup that is easilyimplemented for a variety of driveline setups. FIGS. 2 and 3 depict flowcharts illustrating methods for diagnosing mechanical component faults.FIG. 4 shows a lookup truth table for identifying unauthorized clutchconditions. FIG. 5 illustrates ranges of operating conditions that mayindicate a mechanical component fault. FIGS. 6 and 7 depict timingdiagrams of use-case control and diagnostic strategies for identifyingfault conditions and operating a driveline component in a fault state,to avoid unwanted vehicle behavior.

FIG. 1 is a schematic illustration of a control and diagnosticarchitecture for a vehicle 100. The vehicle 100 may be a light, medium,or heavy duty vehicle designed for on and/or off-road travel. Toelaborate, the vehicle may include a power source such as an internalcombustion engine, an electric machine 104 (e.g., motor-generator),combinations thereof, and the like. Thus, the vehicle may be a hybridvehicle or a battery electric vehicle (BEV), such as a single ormulti-speed BEV, in different examples. Alternatively, the vehicle maybe a combustion engine vehicle, and the electric machine 104 may beomitted.

A driveline controller 102, a driveline system 106 with a plurality ofmechanical vehicle components, and an input device 108 may reside in asystem 110 of the vehicle 100. The system 110 further includes adiagnostic controller 112 in communication with a driveline controller102, driveline system 106, and an input device 108. These components maybe in electronic communication (e.g., wired and/or wireless electroniccommunication) with one another to facilitate data transfertherebetween. The diagnostic controller 112 represents a driveline guardand may include a plurality of logic modules for monitoring andpreventing a fault (e.g., unintended behavior) in the system 110, whichwill be discussed further with reference to FIG. 2. In one example, thediagnostic controller 112 and the driveline controller 102 may bedistinct components which may be spaced away from one another.

In one example, the driveline controller 102 and the diagnosticcontroller 112 may each include a processor 114, 116 and a memory unit118, 120, respectively, holding instructions stored therein that whenexecuted by the processor cause the controller to perform variousmethods, control techniques, etc. described herein. The processors 114,116 may include one or more processing units and/or other suitable typesof circuits. The memory units 118, 120 may include known data andstorage mediums, such as random access memory, read only memory, keepalive memory, combinations thereof, etc. The memory units 118, 120 maybe distinct devices that execute separate logic modules (e.g., adriveline control module and a diagnostic module, respectively), in oneexample. The memory devices may therefore be collocated on a commonboard or chip, for instance, or may be spaced away from one another, inalternate configurations. To elaborate, the driveline controller 102 andthe diagnostic controller 112 may be physically separate and distinctfrom the driveline memory unit 118 and diagnostic memory unit 120. Forinstance, the driveline controller and memory unit may be included on afirst circuit board while the diagnostic controller and memory unit maybe included on a second discrete circuit board. As such, the circuitboards may be at least partially housed in separate enclosures, in oneexample, or may be physically separate components collocated in a commonenclosure, in another example. Alternatively, in other examples, asingle controller with a multi-core processor (e.g., dual-coreprocessor) may be used in the system. In such an example, the drivelinecontrol and diagnostic applications may be independently executed viadistinct processing units (e.g., cores) and stored on separate memoryunits. In this way, the driveline control and diagnostic applicationsmay retain independence while the controller achieves a more space andenergy efficient architecture.

The processing unit(s) of the driveline controller 102 or diagnosticcontroller 112 may carry out different nominal control or diagnosticlogic modules, respectively. As described herein, a logic module is aset of instructions (e.g., tasks, algorithms, and the like) thatperforms selected operations, functions, etc. when executed. Drivelinecontroller 102 may include applications designed to implement controlstrategies for the mechanical component in the driveline system 106.Conversely, the diagnostic controller 112 may include applications formonitoring and verifying operation of the mechanical components in thedriveline system 106. In this way, the diagnostic controller may act asa driveline guard. Further, separating the logic modules in this mannerallows the control and diagnostic modules to be independent from oneanother, and may further allow for independent alteration of each,providing increased system adaptability. Further, the adaptabilityresulting from the independence of these applications may allow forefficient integration of diagnostic routines into an existing controlarchitecture, as well as the ability to independently update orotherwise alter diagnostic and/or control architecture.

The components in the driveline system 106 may include an inverter 122,an electric machine 104 (e.g., motor-generator), a gearbox 124 thatincludes one or more clutches 126 and gears 128, a differential 130,etc. The electric machine 104 may be a motor for generating rotationalenergy to be transferred to vehicle wheels via an axle shaft, and maytherefore include a rotor, stator, housing, and the like. In oneexample, the electric machine 104 may be a motor-generator which may actas a motor for generating rotational energy, and, conversely, as agenerator for receiving rotational energy and transforming it intoelectrical energy.

The electric machine 104 may be an alternating current (AC) type motoror motor-generator, such as a multi-phase motor (e.g., three, six, ornine phase motor). In the case of a multi-phase motor or other suitableAC motor, electrical inverter 122 (e.g., multi-phase inverter such as athree, six, or nine phase inverter that matches the phases of the motor)is implemented to convert direct current (DC) power from a power source(e.g., battery, capacitor, other suitable energy storage devices, etc.)to AC power for consumption by the electric machine 104. Conversely,when the electric machine 104 acts as a generator, the inverter 122 mayconsume AC power and convert it to DC power to be stored in a suitableelectric storage device, such as the aforementioned power source.Additionally, a sensor coupled to or integrated into the inverter 122may be able to detect the torque applied by the electric machine 104 tobe used at the diagnostic controller 112 in determining a faultcondition, as will be described in further detail herein. For instance,a current sensor may be integrated into the inverter and designed tomeasure the current delivered to the electric machine. In turn, theelectric machine's torque may be inferred from this current measurement.In other examples, when an internal combustion engine is used as themotive power source for the vehicle, the electric machine 104 and theinverter 122 may be omitted.

The driveline may further include a gearbox 124 with one or moreclutches 126 and gears 128. Specifically, in one example, the gearboxmay include five clutches which may open and close to activate anddeactivate different set of gears. However, numerous gearbox and clutcharrangements have been contemplated. The gearbox 124 may be rotationallycoupled to the electric machine 104, in one example. However, in analternate example, the electric machine 104 may directly provide powerto a drive wheel without a gearbox or other transmission componentstherebetween.

The clutches 126 may be engaged or disengaged to place the vehicle inforward, reverse, and neutral modes. Alternatively, for sometransmissions, particularly those utilizing one or more electricmachines as a power source, there may be no difference in clutchsettings between forward and reverse modes, where the direction oftravel is dictated by the direction of rotation of the electric machine.In other examples, the gearbox may have discrete gear ratios in theforward drive mode, as well as the reverse drive mode, in some cases. Assuch, the transmission is able to create different gear ratios tooperate the vehicle in the aforementioned modes. For instance, thegearbox may have two or more discrete gear ratios which may be operatorselectable and/or programmatically selected by the driveline controllerbased on vehicle speed and/or load. The gearbox 124 may be included in atransmission 125. In some examples, the transmission may be adual-clutch automatic transmission (DCT), employing two input clutcheswhich connect a pair of input shafts to a motive power source (e.g.,engine, motor, motor-generator, etc.). One of the input clutches is usedto drive even-numbered gears, while the other input clutch is used todrive odd-numbered gears. Further, in the DCT, synchronizers may beemployed to establish power transfer between the input shafts and thetransmission output. In some cases, the DCT may be a powershifttransmission. Still further in some examples, the transmission mayinclude more than two clutches, such as five clutches, for instance. TheDCT is able to efficiently switch between gears by timing the operationof one clutch to engage as the other is disengaging so that there is nointerruption of torque supply to the wheels during shifting, where thecapability for smooth transitions between gear ratios may enhancevehicle drivability and shift quality. Additionally, or alternatively,the transmission 125 may a hybrid transmission with an integratedelectric machine.

The gearbox 124 may be mechanically coupled to an axle for transmittingmechanical power to drive wheels. The gearbox 124 may receive mechanicalpower from, or transfer mechanical power to, the electric machine 104(e.g., motor-generator) via a driveshaft and/or other suitablemechanical components. In some cases, the gearbox 124 may transfermechanical power to or receive mechanical power from differential 130.The differential 130 may then transfer mechanical power to or receivemechanical power from the drive wheels via left and right axle shafts.The differential 130 may be a locking differential, an electronicallycontrolled limited slip differential, or a torque vectoringdifferential, for example. When the differential has lockingfunctionality, the differential may be operated in a locked or anunlocked configuration via a locking clutch 133 to selectively transfermechanical power to or receive mechanical power from vehicle drivewheels via left and right axle shafts, in some cases.

The components in the vehicle system 110 may be monitored for faults bythe diagnostic controller 112. The input device 108 is designed toreceive operator input and responsively generate an input signal orcommand that is transmitted to the driveline controller 102 forcontrolling operation of one or more of the mechanical vehiclecomponents within driveline system 106 described above. Hence, the inputdevice 108 allows a vehicle operator to request adjustment of a vehicleoperating parameter such as clutch configuration (e.g., open or closed),motor power, motor speed, engine power, engine speed, differentialconfiguration (e.g., a locked or an unlocked configuration), etc.Examples of the input device include a drive pedal, gear selector, gearstick, clutch pedal, buttons, knobs, touch interfaces, combinationsthereof, and the like.

The drive pedal (e.g., throttle pedal) may generate a signal indicativeof a power request. During normal operation, the driveline controllermay adjust the electric machine 104 and/or the inverter 122 to achieve apower set-point or range correlated to the operator power request.

Further, the operator may interact with the gear selector (e.g., aReverse-Neutral-Drive shift selector), to select a drive mode (e.g.,reverse drive, neutral, or forward drive). In a normal operating mode,responsive to selection of the drive mode, the driveline controller 102may control the gearbox 124 to open or close one or more clutches 126 toplace the gearbox in the selected mode. Alternatively, the drivelinecontroller may adjust the electric machine to place the powertrain inthe selected mode. In yet another example, the input device may includea differential actuator that initiates differential locking andunlocking operations. Hence, in the above described examples, a vehicleoperator may request adjustment in wheel torque/power, transmission gearselection, differential configuration, etc. at their predilection,whereby, in a nominal mode of operation, the driveline controller 102adjusts components in the driveline system responsive to the adjustmentof the input device. However, more automated control strategies of atleast a portion of the driveline components may be implemented, in otherexamples.

Although the driveline controller 102 receives requests from the inputdevice 108 to control operation of the various mechanical vehiclecomponents described herein, the diagnostic controller also monitorsthese requests and verifies if the control settings match a predefinedset of undesired settings. Specifically, the diagnostic method may nottake into account intended component settings and instead focus oncomparing the actual settings with a predefined set of unwantedsettings, to simplify diagnostics. When one of the control settingsmatches one of the undesired settings in the predetermined set, thediagnostic controller 112 may override the driveline controller 102 inorder to operate the mechanical vehicle component in an active faultstate. In one example, the diagnostic controller, upon identifying afault condition (e.g., an unverified condition), may trigger an activefault state, as indicated at 144, by removing the closing force appliedto the one or more clutches to bring them into an opened state, thusinhibiting transfer of power through the clutches. This command mayoverride a driveline control command to disengage the clutches orsustain disengagement of the clutches. In this way, unintended vehicleacceleration or deceleration may be circumvented.

In another example, upon identifying a fault condition, the diagnosticcontroller 112 may trigger an active fault state by interrupting thetransfer of AC power from the inverter 122 to the electric machine 104(e.g., by opening one or more switches in the inverter 122 or otherwisedecreasing the electric power flow from the inverter to the electricmachine). As such, current flow from the inverter to the electricmachine may be stopped or significantly decreased when the faultcondition is identified. In yet another example, when the component isdifferential 130, the diagnostic controller, upon identifying a faultcondition, may trigger an active fault state by unlocking thedifferential. By allowing the diagnostic controller 112 to override thenominal control commands from the driveline controller 102 during afault condition, the system may effectively and efficiently executediagnostic routines with higher accuracy to quickly discontinue or avoidundesired kinematic behavior of the vehicle.

In FIG. 1, linear arrows characterize the high level data flow patternin the system. To elaborate, arrows 132, 134 indicate the transfer ofdata between the input device 108 and the driveline system 106,respectively, and the driveline controller 102. Additionally, arrow 136indicates the transfer of data between the driveline controller 102 andthe driveline system 106. Arrows 138, 140 indicate the transfer of dataredirected from input device 108 and from driveline controller 102,respectively, to the diagnostic controller 112. Arrow 142 indicates thetransfer of data from the diagnostic controller 112 to the mechanicalvehicle component of the driveline system 106, for triggering an activefault state 144. As such, each arrow indicates data that may be sentfrom controller hardware to a vehicle component and received by saidvehicle component, or vice versa.

The driveline controller 102 and/or diagnostic controller 112 mayreceive inputs from sensors such as a current sensor 123 coupled to orintegrated within the inverter 122, one or more clutch positionsensor(s) 127, an input device position sensor 109, an electric machinespeed sensor 105, a differential position sensor 131, and the like. Insome examples, both the driveline controller and/or diagnosticcontroller may receive sensor inputs in parallel. In one example, thedriveline controller 102 may receive the sensor signals and relay thesesignals to the diagnostic controller 112. Alternatively, at least aportion of the sensor signals may be sent in parallel to the diagnosticcontroller 112 and the driveline controller 102.

FIG. 2 illustrates a method 200 for vehicle system operation and faultdiagnostics. The method 200 as well as other methods described hereinmay be executed by the diagnostic controller 112, driveline controller102, and vehicle system 110 shown in FIG. 1. Alternatively, the method200 and/or the other methods described herein may be implemented byother suitable controllers, vehicle system, and corresponding componentsor by a common controller with multiple processors and memory units thatseparately execute control and diagnostic modules. Further, theinstructions for carrying out the method 200 and the rest of the methodsdescribed herein may be executed by one or more controllers based oninstructions stored on different memory units and in conjunction withsignals received from the vehicle system. The controller(s) may employactuators of the vehicle system to adjust vehicle operations, accordingto the methods described below.

At 202, the method collects vehicle operating data from variouscomponents in the vehicle system, via a capture unit of a controller,for example. The method 200 may determine vehicle operating data basedon output from various sensors and actuators described herein. In someexamples, the capture unit determines an input device state. In oneexample, a drive device (e.g., throttle pedal) request from a vehicleoperator may be determined via a throttle pedal sensor. In anotherexample, a position of a gear selector (e.g., R-N-D shifter) may be usedto determine a gear selector request. The capture unit may furtherdetermine a torque applied by the electric machine (e.g.,motor-generator), which may be inferred from an inverter current flow.The capture unit may further determine the position of one or moreclutches, and an actual vehicle speed measured via a speed sensor.

At 204, the method determines whether the measured actual vehicle speedis below a speed threshold value. The speed threshold may be a fixedvalue or a dynamic value that may be adjusted depending on theapplication and/or vehicle operating environment. In some examples, thespeed threshold value may be a relatively low or medium vehicle speed,such as approximately 1 meters per second (m/s) or 5 m/s.

It will be understood that when vehicle speed is below the threshold, afault leading to unintended vehicle movement may be noticeable by theoperator and thus may demand the calculation (e.g., prediction) of wheeltorque. In other words, when a low vehicle speed is determined, wheeltorque is then slated for calculation. On the other hand, when vehiclespeed exceeds the threshold, unintended vehicle acceleration ordeceleration may be less noticeable by the operator. For example, athigher speeds, changes in vehicle speed caused by erroneous clutchsettings may be substantially unperceivable. As a result, at higherspeeds the wheel torque calculation and subsequent diagnostic steps maybe circumvented. In this way, the system focuses on preventingunintended vehicle behavior based on a torque monitoring function, asopposed to relying on a torque setting function of an invertercontroller coupled to an electric machine to identify a fault condition,thus providing an efficient cost-effective system for avoiding unwantedbehavior by eliminating the need for costly inverter controllerdevelopment. As such, the driveline system described herein may placeconstraints on the torque monitoring settings of the electric machine asopposed to the torque setting functions.

If the vehicle speed exceeds the speed threshold value (NO at 204), themethod moves to 206 where the method maintains the current vehicleoperating strategy. In order to maintain the current vehicle operatingstrategy, a driveline controller may continue to send control commands,based on operator input from an input device or through automaticcontrol routines, to various mechanical vehicle components of thedriveline system. In some instances, this may involve continuing toaugment power supplied to the electric machine based on an increaseddrive pedal (e.g., throttle pedal) input, or, in other instances, mayinvolve opening or closing clutches to achieve a desired gear ratio asdictated by a gear selector input, vehicle speed, and/or vehicle load.

Conversely, if the vehicle speed is below the speed threshold value (YESat 204), the method moves to 208, where the method determines (e.g.,predicts) the torque applied at the vehicle wheels, also referred to asthe wheel torque. For example, wheel torque may be derived from thetorque of one or more electric machines, which may be depend up thecurrent supplied to the electric machines from an inverter. Further,this calculation may take into account the one or more clutch positions,as determined at 202, and the specific gearbox configuration. Forinstance, the clutch positions may be mapped to the active gear ratio inthe gearbox and said gear ratio may be used along with electric machinetorque to calculate the drive wheel torque. Further, the applied wheeltorque may be determined to be zero if the gearbox includes a neutralclutch in an open position. However, in alternate configurations, whenan electric machine is coupled directly to the output of a vehicle wheelshaft, the clutch positions may not be taken into account whenpredicting wheel torque. In these configurations, the drive wheel torquemay be determined via a fixed multiplication of the electric machinetorque and the output shaft reduction ratio.

At 210, the method determines if the calculated wheel torque is above atorque threshold value (e.g., a positive non-zero value). The torquethreshold may be a fixed or dynamic value, depending on the applicationand/or vehicle operating environment. The torque threshold may be arelatively low torque value. Further, the torque threshold may bespecific to a vehicle type (e.g., commercial vehicle, passenger vehicle,etc.) and selected to cause the vehicle to begin moving from astandstill on a flat surface. For example, when the vehicle is a truck,the torque threshold may be 50 Newton-meters (Nm), wherein a torquebelow the torque threshold will not cause the vehicle to move. In otherexamples, however, such as when a method is used to guard againstunintended vehicle acceleration while the vehicle is moving, a torquethreshold may be significantly higher (e.g., 200 Nm), corresponding to atorque that would cause unwanted acceleration at higher vehicle speeds.

If the wheel torque is below the torque threshold (NO at 210), themethod again moves to 206. Conversely, if the wheel torque exceeds thetorque threshold (YES at 210), the method moves to 212 where the methoddetermines if the wheel torque is in a direction opposite the intendeddirection or if an operator power request exceeds a threshold value. Themethod may judge if the wheel torque is in an opposite direction thanintended to ascertain if the vehicle is traveling in a direction that isopposite than what is intended. On the other hand, the method may judgeif the operator power request exceeds the threshold value to ascertainif undesired longitudinal accelerator of the vehicle is occurring. Insome examples, the method may utilize clutch positions along with thewheel torque to determine if the wheel torque is in a direction oppositethe intended direction. However, in some cases, such as where one ormore electric machines are implemented to power vehicle driveoperations, monitoring clutch settings to determine the wheel torque andthe direction thereof may be forgone as there is no difference in clutchsettings in forward and reverse drive modes, in such an example. Inthese cases, the direction of vehicle movement may be determined by thedirection of the electric machine torque. By calculating and verifyingthe actual wheel torque and direction of torque applied by the electricmachine for fault monitoring, as opposed to monitoring actual clutchsettings, a reliable system is provided for diagnosing a fault conditionin a variety of driveline configurations.

The power request threshold may be a predetermined value, in oneexample. Further, the power request may be expressed as a percentage ofthrottle pedal depression, such that zero power request corresponds to0% throttle depression. The power threshold may be a zero power requestor a relatively low value, such as 15%, 20%, or 25% pedal depression, incertain use-cases.

If the wheel torque is in the intended direction or the operator powerrequest is not greater than the threshold value (NO at 212), the methodmoves to 206. However, if the wheel torque is determined to be in adirection opposite the intended direction or the operator power requestis greater than the threshold value (YES at 212), a fault condition isidentified and the method moves to 216.

When step 212 judges if the power request exceeds the threshold, method200 provides efficient and confident identification of a fault conditionwhere excessive drive torque is applied to the vehicle wheels in thecase of no or low throttle demand, which may result in unintendedlongitudinal vehicle acceleration. Alternatively, when step 212 judgesif the wheel torque is in the opposite direction as intended, method 200provides rapid and robust identification of a fault condition where thevehicle is traveling in an opposite direction.

At 216, the method determines the duration of the fault condition (e.g.,the time passed since identification of the fault condition), asdetermined in the aforementioned steps, and verifies the fault durationagainst a fault tolerant time. The fault tolerant time may be apredetermined value or may be configurable depending on the applicationor operating environment. Further, the fault tolerant time may define aduration of time beyond which the mechanical vehicle component operationmay lead to unintended kinematic behavior that is perceivable by theoperator. Further, the fault tolerant time may be chosen so as toprevent misidentification of a fault condition by selecting a time thattakes into account component control latency and/or driveline componentcharacteristics. For example, some transmissions may experience a delayin engagement of clutches and gears during a shift event. The faulttolerant time may take this delay into account and allow for some lag inengagement before triggering an active fault state, as shiftingtransients may not be indicative of unintended vehicle behavior. Using afault tolerant time as an entry condition for activation of a faultstate allows the current system to avoid mistakenly identifying a faultcondition and/or operating the component in an active fault state whencompared to other systems that may instantaneously activate a fault modewhen the driveline component settings do not match monitored values.

If the fault duration is less than the fault tolerant time (NO at 216),the method moves to 206 where the method maintains the current vehicleoperating strategy. For instance, the driveline component may continueoperation in a nominal mode where it is adjusted based on operatorrequested torque and vehicle load, for instance. After 206, the methodreturns to 202. However, if the fault duration exceeds the faulttolerant time (YES at 216), the method continues on to 218.

At 218, the diagnostic controller triggers an active fault state of themechanical vehicle component. Thus, at 220, the mechanical vehiclecomponent is operated in the active fault state. Operating the componentin the fault state, via a diagnostic controller, may include overridingnominal control commands generated by the driveline controller. Forexample, when the mechanical component is a plurality of clutches, thenominal control command may be to sustain clutch engagement and thefault state may be implemented by removing either all or most of thetorque applied to the vehicle wheels by removing the closing force ofthe clutches, to bring the clutches into an opened state. In otherexamples, where the mechanical component is an electrical inverter, thefault state may be realized by overriding a nominal control command tosupply the motor with AC power from the inverter, thus interrupting(e.g., halting or significantly inhibiting) the transfer of AC powerdelivered to the electric machine from the inverter. For instance, oneor more switches in a multiphase inverter may be opened to decrease thepower transfer to the electric machine. In this way, unintended vehiclecomponent behavior that may cause unwanted vehicle motion may be quicklyidentified and discontinued. Consequently, the driveline system providesmore predictable performance, as perceived by the operator. When themechanical component is a differential locking clutch, operating thelocking clutch in the fault state may include disengaging the clutchwhich may override a command to lock the differential.

FIG. 3 shows another method 300 for fault diagnostics of clutches in avehicle system. At 302, the method collects vehicle operating data fromthe vehicle system via a capture unit of a controller. For example, aspeed sensor may be used to measure an actual vehicle speed. Further, at302, the controller determines the position of one or more clutches(e.g., whether each clutch is in an opened or closed state). Toelaborate, the gearbox's clutch settings may be identified as eitherengaged or disengaged. Further, in certain cases, the clutch settingsmay be identified as being partially engaged or disengaged.

At 304, the method verifies the clutch settings against a lookup truthtable to identify a fault condition. The lookup truth table may includeupper and lower vehicle speed thresholds that correspond to clutchpositions that may invalidate the clutch settings. In other examples,the lookup truth table may indicate other ranges of operating parametersto identify unauthorized conditions. The truth table may thereforeexpress sets of conditions (e.g., clutch positions, vehicle speeds,etc.) that are unwanted. One exemplary truth table is described ingreater detail herein with regard to FIG. 4. Next, at 306, adetermination is made as to whether or not the operating conditions areauthorized.

If the vehicle speed and clutch positions are authorized based on thetruth table verification (YES at 306), the method moves to 308 where thecurrent vehicle operating strategy is maintained, such that, forinstance, clutch positions are controlled by commands from a drivelinecontroller. If the vehicle speed and clutch positions are determined tobe unauthorized (NO at 306), a fault condition is identified and themethod moves to 312.

At 312, the method determines the duration of the fault condition (e.g.,the time passed since the identification of the fault condition), asdetermined in the aforementioned steps, and verifies the fault durationagainst a fault tolerant time, as previously described. If the faultduration is less than the fault tolerant time (NO at 312), the methodmoves to 308 to maintain the current vehicle operating strategy.However, if the fault duration exceeds the fault tolerant time (YES at312), the method continues to 314. Using the fault tolerant time permitsdiagnostic confidence to be further increased.

At 314, the method triggers an active fault state in the plurality ofclutches. Thus, at 316, one or more of the clutches is/are operated inthe active fault state. Again, operating the clutches in an active faultstate may include opening the clutches to inhibit torque transfer fromthe transmission to the drive wheels and overriding a command to closethe clutches. Operating a clutch for a differential locking device mayinclude opening a locker clutch to discontinue differential locking.Method 300 enables unauthorized clutch setting which may lead tounanticipated vehicle deceleration to be quickly and confidentlydetermined. Subsequent to the rapid determination of the unauthorizedclutch positions, steps are taken to discontinue the unauthorized clutchsettings. Unanticipated changes in driveline performance may thereforebe mitigated.

FIG. 4 depicts an exemplary lookup truth table 400 for verifying avehicle speed against clutch settings. The lookup truth table 400 may bestored in a memory unit of a diagnostic controller (e.g., the memoryunit 120 and diagnostic controller 112, shown in FIG. 1). Rows of thelookup truth table 400 are populated with lower and upper speedthresholds that correspond to a plurality of unauthorized clutchposition settings (e.g., open or closed). To elaborate, unauthorizedclutch position settings are provided for five clutches, A-E, duringvehicle operation within predefined vehicle speed ranges. However,lookup truth tables with an alternate number of clutches may be used, inother examples.

In a diagnostic routine, the diagnostic controller may determine avehicle speed and a plurality of clutch position settings, and comparethe speed and clutch position settings against the lookup truth table inorder to determine unverified conditions indicative of a faultcondition. In other words, the diagnostic controller may use lookuptruth table 400 to verify actual vehicle settings against a predefinedand constrained set of unauthorized settings. In this way, a simpler andmore reliable system is provided for diagnosing the mechanical componentwhen compared to diagnostic systems that determine requested or intendedcomponent settings against actual component settings. When verifyingvehicle speed and clutch positions against lookup truth table 400,multiple clutch conditions may lead the diagnostic controller todetermine an unauthorized setting is present. For instance, the lookuptruth table 400 in a first row 402 indicates, in one example, a lowerspeed threshold of −10 m/s, and an upper speed threshold of 5 m/s. Whenthe vehicle travels at a speed between −10 m/s and 5 m/s, an unverifiedclutch condition may be identified if: clutch A is closed, clutch B isclosed, and clutch D is open. In the second row 404 of the lookup truthtable, an unauthorized setting conclusion may be reached when thevehicle speed is between −10 m/s and −1 m/s and clutch A is closed,clutch B is closed, and clutch D is closed. In the third row 406 of thelookup truth table, the controller may determine that an unauthorizedsetting is occurring when the vehicle speed is greater than 1 m/s andclutches C and D are both closed.

In other examples, a single clutch condition may lead to an unauthorizedsetting conclusion. For instance, in the third row of the lookup truthtable when the vehicle speed is greater than 1 m/s and clutch E isclosed, the diagnostic controller may judge that an unauthorized clutchsetting is occurring. Further, an unknown or indeterminable clutchposition may be considered an unverified condition. Even further, anunknown or indeterminable vehicle speed may also be considered anunverified condition indicative of a fault.

The diagnostic controller may recognize any of the aforementionedsettings as a fault condition, and may trigger an active fault state tooperate the clutches in a fault mode (e.g., by opening one or more ofclutches A-E). The truth table 400 allows for confident diagnosis of theclutches by providing unverified conditions known to cause unwantedchanges in vehicle kinematic performance (e.g., unintended vehicleacceleration/deceleration). Thus, the diagnostic routine may not relysolely on comparing intended clutch settings against actual clutchsettings, which may lead to unwarranted triggering of the fault statethat may hamper vehicle performance, and a more efficient and reliablediagnostic routine that guards against unacceptable clutch conditions ispossible.

FIG. 5 shows a diagram 500 which illustrates ranges of vehicle operatingconditions that may indicate a mechanical component fault. Diagram 500includes a horizontal axis which indicates a drive device input from anoperator, such as a throttle pedal position. The throttle pedal positionis represented as a percentage of throttle pedal depression, increasingalong the horizontal axis in the direction of the arrow. Diagram 500further includes a vertical axis indicating a wheel torque applied atthe vehicle drive wheels, increasing to a maximum torque value in thedirection of the arrow. Diagram 500 also includes a throttle threshold506 and a torque threshold 508.

Vehicle operating conditions where the wheel torque exceeds torquethreshold 508 and throttle pedal depression is less than throttlethreshold 506, shown at region 502, may be recognized as unauthorizedsettings, which may lead to unintended longitudinal vehicleacceleration. To elaborate, a relatively low throttle request (belowthrottle threshold 506) may indicate that vehicle acceleration is notdesired, such that excessive wheel torque (above torque threshold 508)may lead to unwanted acceleration. Thus, a throttle request and wheeltorque falling within region 502 may be recognized by a diagnosticcontroller as a fault condition, and the diagnostic controller may,after the fault tolerant time is exceeded, operate the mechanicalcomponent in a fault state, in order to discontinue or altogether avoidunwanted vehicle acceleration. Triggering the active fault state mayinclude, in some cases, bringing the gearbox clutches into an open stateso as to prevent further transfer of power to the vehicle drive wheels,thus reducing the chance of further unintended acceleration.

Also shown in FIG. 5 is a region 504, which indicates a range ofoperating conditions in which unintended torque transfer between themotor and the wheels is occurring but is controllable. Therefore, unlikefault region 502, when the driveline is operating under conditionswithin region 504, control settings may be altered as opposed tooperating the driveline component in a fault state. Specifically, region504 depicts a scenario where a throttle request exceeds throttlethreshold 506. Therefore, in region 504 the torque request may beremoved to avoid unintended acceleration. Thus, for vehicle operatingconditions falling within region 504, it may not be desirable to triggeran active fault state of a mechanical vehicle component. It is thereforepossible to avoid superfluous triggering of the active fault state whichmay degrade vehicle performance.

Diagram 500 further indicates a creep torque, as shown via a dashedline. In some cases, a small amount of creep torque may be applied atthe vehicle wheels in the case of a 0% throttle request. Torquethreshold 508 is selected so as to be greater than the creep torquelevel, as the small amount of creep torque applied may not warrant faultmode activation. Hence, the system may further avoid unwarrantedtriggering of the active fault state.

FIG. 6 illustrates a timing diagram 600 of a use-case diagnostic controlstrategy for a mechanical vehicle component. In each plot of the timingdiagram, time is indicated on the abscissa and increases in thedirection of the arrow. The ordinate for plot 602 indicates the level ofelectric power transferred from the inverter to the electric machine,and the ordinate for plot 608 indicates the fault state (activated anddeactivated). The ordinate for plot 604 indicates torque applied to thewheels, which increases in the direction of the arrow. The ordinate forplot 606 indicates a throttle pedal position, which may be expressed asa percentage of throttle pedal depression which increases in thedirection of the arrow. The ordinate for plot 609 indicates a vehiclespeed that increases in the direction of the arrow. FIG. 6 also shows atorque threshold 610, and a throttle threshold 612 (e.g., 15%, 14%, or12%), and a vehicle speed threshold 614 (e.g., 5 m/s, 3 m/s, or 1 m/s).

From t0 to t1, vehicle speed is less than the threshold 614, throttlepedal depression is less than the threshold 612, and the inverter beginsto transfer AC power to the electric machine. Thus, the applied torqueincreases from t0 to t1. However, when the applied torque surpasses thetorque threshold 610 at t1, and the throttle pedal position remainsbelow the threshold 612, the diagnostic controller recognizes that anunauthorized condition is occurring.

From t1 to t2, the diagnostic controller measures the duration of theunauthorized condition. The time between t1 and t2 may be the faulttolerant time described above, which may be implemented as an entrycondition for the fault state of the inverter. At t2, the duration ofthe unauthorized condition meets the fault tolerant time, and thediagnostic controller triggers an active fault state where the AC powerdelivered by the inverter to the electric machine significantly andabruptly decreases. In this way, the torque applied at the wheels mayalso decrease, and undesired vehicle acceleration caused by theinteraction between the inverter and the electric machine is avoided. Insome cases, the applied torque may decrease to a level below thethreshold 610, yet the controller may continue to recognize the vehicleoperating condition(s) as unauthorized when the throttle pedaldepression remains below the threshold 612.

From t2 to t3, the throttle pedal depression increases and the appliedtorque continues to increase accordingly, as the fault state remainsactivated. However, when the throttle pedal position (e.g., request)surpasses throttle threshold 612 at t3, the diagnostic controllerdeactivates the fault state, and the inverter may resume normal transferof AC power transfer to the electric machine.

FIG. 7 illustrates another timing diagram 700 of a use-case diagnosticcontrol strategy for a mechanical vehicle component. In each plot of thetiming diagram, time is indicated on the abscissa and increases in thedirection of the arrow. The ordinates for plots 702, 703 indicate theactual clutch position setting (open and closed) of a first clutch and asecond clutch, and the ordinate for plot 704 indicates the vehiclespeed, which increases in the direction of the arrow. The ordinate ofplot 708 indicates the fault state (activated and deactivated). FIG. 7also shows lower and upper vehicle speed thresholds 710 and 712,respectively.

From t0 to t1, vehicle speed increases while in the first and secondclutches are closed. In some cases, a diagnostic controller maydetermine the vehicle speed and the clutch positions and verify thesesettings against a lookup truth table, such as table 400 shown in FIG.4, to identify unauthorized clutch positions indicative of a drivelinefault.

At t1, the vehicle speed enters a region between the lower speedthreshold 710 and the upper speed threshold 712, and the diagnosticcontroller recognizes that the while the clutches are closed and withinthe speed range between the upper and lower an unauthorized setting isoccurring. Thus, the diagnostic controller recognized that anunauthorized clutch condition is present.

From t1 to t2, the diagnostic controller measures the duration of theunauthorized settings. The time between t1 and t2 may be the faulttolerant time described above, which may be used as an entry conditionfor activating the fault state of the first and second clutches. At t2,the duration of the fault state reaches the fault tolerant time, thefault state is activated by operating the plurality of clutches in anopen state. After t2, as the vehicle speed remains above lower speedthreshold 710 and below upper speed threshold 712, the fault stateremains active, and the clutches are maintained in an open position.Thus, invalid clutch setting may be quickly and confidently recognizedusing the unauthorized clutch positions mapped to a speed range and thendiscontinued to reduce the likelihood of unwanted vehicle decelerationor acceleration.

The technical effect of the driveline systems and methods describedherein is to efficiently and confidently diagnose driveline faultsthrough the use of a predetermined set of unauthorized componentsettings and avoid unwanted vehicle behaviors that may causeunanticipated changes in driveline performance such as unintendedacceleration or movement of the vehicle in an unintended direction.

The invention will be further described in the following paragraphs. Inone aspect, a method is provided for operation of a vehicle system,comprising: at a diagnostic controller or processing unit independentfrom a driveline controller or processing unit, respectively,determining vehicle speed from a vehicle speed sensor; determining aposition of a plurality of clutches in a transmission of the vehiclesystem; identifying an unauthorized clutch state based on the clutchpositions and a vehicle speed; and responsive to the identification ofthe unauthorized clutch state, operating the plurality of clutches in afault state. In one example, the unauthorized clutch position may beidentified by comparing the vehicle speed and the clutch positionagainst a lookup truth table; and rows of the lookup truth tablecomprise lower and upper speed thresholds corresponding to a pluralityof unauthorized clutch position settings. In another example, theplurality of clutches may be operated in the fault state only when theunauthorized clutch state exceeds a fault tolerant time. In yet anotherexample, the fault tolerant time may be a fixed value. In anotherexample, the steps of determining the vehicle speed, determining thevehicle speed, determining the position of the plurality of clutches,identifying the unauthorized clutch state, and operating the pluralityof clutches in the fault state may be implemented by the diagnosticcontroller distinct from the driveline controller. In another example,the method may further include, at the driveline controller while theplurality of clutches are not in the unauthorized clutch state,operating the plurality of clutches based on operator instructions withan input device. In another example, the steps of determining vehiclespeed, determining the position of the plurality of clutches,identifying the unauthorized clutch state, and operating the pluralityof clutches in the fault state are implemented by the diagnosticprocessing unit distinct from a driveline processing unit and whereinthe diagnostic processing unit and the driveline processing unit areincluded in a vehicle controller. In another example, operating theplurality of clutches in the fault state may include disengaging one ormore of the plurality of clutches. In another example, the plurality ofclutches may be operated in the fault state by overriding commands fromthe driveline controller or processing unit.

In another aspect, a method is provided for operation of a vehiclesystem. The method comprises at a diagnostic controller independent froma driveline controller, determining vehicle speed from a vehicle sensor;determining a position of a plurality of clutches in a transmission ofthe vehicle system; identifying an unauthorized clutch state bycomparing the vehicle speed and the clutch positions against a lookuptruth table; and responsive to the identification of the unauthorizedclutch state and when the unauthorized clutch state exceeds a faulttolerant time, operating the plurality of clutches in a fault state. Inone example, rows of the lookup truth table may comprise lower and upperspeed thresholds corresponding to a plurality of unauthorized clutchsettings. In another example, operating the plurality of clutches in thefault state may include disengaging one or more of the plurality ofclutches by overriding commands from the driveline controller to preventtorque transfer to a plurality of drive wheels from the transmission. Inyet another example, the plurality of clutches may be included in anautomatic transmission or a hybrid transmission.

In yet another aspect, a vehicle system is provided that comprises atransmission including a plurality of clutches selectively engaging anddisengaging to place the transmission in one of a plurality of discretegear rations; a diagnostic controller or processing unit including:instructions that when executed cause the diagnostic controller orprocessing unit to: determine a vehicle speed from a vehicle speedsensor; determine a position of the plurality of clutches; and identifyan unauthorized clutch state based on the clutch positions and a vehiclespeed; and instructions that when executed, while the unauthorizedclutch state persists longer than a fault tolerant time, cause thediagnostic controller or processing unit to: operate the plurality ofclutches in a fault state.

In any of the aspects or combinations of the aspects, the unauthorizedclutch position may be identified using a lookup truth table.

In any of the aspects or combinations of the aspects, in the lookuptruth table, a single condition may be used to identify the unauthorizedclutch state.

In any of the aspects or combinations of the aspects, the fault toleranttime may be dynamic and is adjusted based on one or more vehicleoperating conditions.

In any of the aspects or combinations of the aspects, the transmissionmay be an automatic transmission.

In any of the aspects or combinations of the aspects, the transmissionmay be a hybrid transmission.

In any of the aspects or combinations of the aspects, the plurality ofclutches may comprise a locking clutch included in a differential.

In another aspect, a method is provided for operation of a vehiclesystem with an electric machine, comprising: at a diagnostic controlleror processing unit independent from a driveline controller or processingunit, respectively, determining an input device state and an electricmachine torque; determining a fault condition of a vehicle componentbased on the input device state and the electric machine torque; and inresponse to determining the fault condition, triggering a fault state ofthe vehicle component and controlling the vehicle component in a faultmode. In one example, the steps of determining the input device state,determining the fault condition, and triggering the fault state may beimplemented in a diagnostic core independent from a driveline core in avehicle controller; and controlling the vehicle component may includeoverriding control commands from the driveline core. In another example,the steps of determining the input device state, determining the faultcondition, and triggering the fault state may be implemented in thediagnostic controller independent from the driveline controller; andcontrolling the vehicle component may include overriding controlcommands from the driveline controller. In yet another example, theinput device state may be a power request; and the method may furthercomprise: determining a predicted wheel torque based on the electricmachine torque; and determining the fault condition determining thefault condition may include determining that a fault condition isoccurring when the predicted wheel torque is greater than a thresholdvalue and the power request is less than a threshold value. In anotherexample, the input device state may be a gear selector position; and themethod may further comprise: determining a predicted wheel torque basedon the electric machine torque; and determining the fault condition mayinclude determining the fault condition is occurring when the predictedwheel torque is greater than a threshold value and is in a directionthat is opposite than a direction selected by the gear selector. Inanother example, the vehicle component may be a gearbox that includesone or more clutches, wherein controlling the gearbox includes openingthe one or more clutches. In another example, the vehicle component maybe an inverter, wherein controlling the inverter in the fault modeincludes decreasing a flow of power from the inverter to the electricmachine. In another example, the step of determining the fault conditionmay be determined while a vehicle speed is less than a threshold value,and the method may further comprise inhibiting the determination of thefault condition when the vehicle speed is greater than the thresholdvalue. In another example, the fault state may be triggered when thefault condition persists for a duration greater than a threshold value.

In another aspect, a method is provided for operation of a vehiclesystem with an electric machine. The method comprises operating adiagnostic processing unit in a controller to: determine an electricmachine torque; derive a wheel torque from the electric machine torque;and responsive to the wheel torque exceeding a threshold value, triggera fault condition corresponding to one of an inverter, electric machine,or gearbox, and overriding control of the inverter, electric machine, orgearbox by a driveline processing unit. In one example, the faultcondition may be triggered when a vehicle speed is less than a thresholdvalue. In another example, the fault condition may be a condition wherewheel direction is opposite of a requested wheel direction.

In another aspect, a vehicle system is provided that comprises adiagnostic controller or processing unit in electronic communicationwith a mechanical vehicle component and including: instructions thatwhen executed cause the diagnostic controller or processing unit to:determine an input device state (e.g., power request {throttle requestfrom throttle pedal} or gear selector position) and an electric machinetorque; and determine the occurrence of a fault condition based on theinput device state and the electric machine torque; and instructionsstored in the memory unit that when, the fault condition is triggered,cause the diagnostic controller or processing unit to: control themechanical vehicle component in a fault state; and override vehiclecomponent control from a driveline controller or processing unit.

In any of the aspects or combinations of the aspects, the input devicestate may be a power request from a pedal; and the occurrence of thefault condition may be determined when a wheel torque derived from theelectric machine torque is greater than a threshold value and the powerrequest is less than a threshold value.

In any of the aspects or combinations of the aspects, the input devicestate may be a position of a gear selector; the occurrence of the faultcondition may be determined when a wheel speed is in a directionopposite than a direction requested by the gear selector; and the wheelspeed may be derived from the electric machine torque.

In any of the aspects or combinations of the aspects, the mechanicalvehicle component may be an inverter, an electric machine, or a gearboxthat includes one or more clutches.

In any of the aspects or combinations of the aspects, when themechanical component may be an inverter, controlling the inverter in thefault state may include decreasing a flow of power from the inverter tothe electric machine.

In any of the aspects or combinations of the aspects, when themechanical component may be a gearbox, controlling the gearbox mayinclude opening the one or more clutches.

In another representation, a driveline system is provided that comprisesa driveline component controller configured to adjust operation of aplurality of clutches in a nominal operating mode and a driveline guardcontroller configured to operate the plurality of clutches in a guardedcondition that overrides the nominal operating mode when the pluralityof clutches are in an unauthorized configuration that correspond to adriveline speed range for a fault duration threshold.

Note that the example control and estimation routines included hereincan be used with various powertrain and/or vehicle systemconfigurations. The control methods and routines disclosed herein may bestored as executable instructions in non-transitory memory and may becarried out by the control system including the controller incombination with the various sensors, actuators, and other powertrainhardware. The specific routines described herein may represent one ormore of any number of processing strategies such as event-driven,interrupt-driven, multi-tasking, multi-threading, and the like. As such,various actions, operations, and/or functions illustrated may beperformed in the sequence illustrated, in parallel, or in some casesomitted. Likewise, the order of processing is not necessarily requiredto achieve the features and advantages of the example embodimentsdescribed herein, but is provided for ease of illustration anddescription. One or more of the illustrated actions, operations, and/orfunctions may be repeatedly performed depending on the particularstrategy being used. Further, the described actions, operations, and/orfunctions may graphically represent code to be programmed intonon-transitory memory of the computer readable storage medium in thepowertrain control system, where the described actions are carried outby executing the instructions in a system including the variouspowertrain hardware components in combination with the electroniccontroller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied tobattery electric vehicles, hybrid vehicle, an internal combustion enginevehicle. Further, engines with V-6, I-4, I-6, V-12, opposed 4, and otherconfigurations may be used. Moreover, unless explicitly stated to thecontrary, the terms “first,” “second,” “third,” and the like are notintended to denote any order, position, quantity, or importance, butrather are used merely as labels to distinguish one element fromanother. The subject matter of the present disclosure includes all noveland non-obvious combinations and sub-combinations of the various systemsand configurations, and other features, functions, and/or propertiesdisclosed herein. It will be apparent to persons skilled in the relevantarts that the disclosed subject matter may be embodied in other specificforms without departing from the spirit of the subject matter. Theembodiments described above are therefore to be considered in allrespects as illustrative, not restrictive.

As used herein, the term “approximately” is construed to mean plus orminus five percent of the range, unless otherwise specified.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A method for operation of a vehicle system, comprising: at adiagnostic controller or processing unit independent from a drivelinecontroller or processing unit, respectively: determining vehicle speedfrom a vehicle speed sensor; determining a position of a plurality ofclutches in a transmission of the vehicle system; identifying anunauthorized clutch state based on the clutch positions and a vehiclespeed; and responsive to the identification of the unauthorized clutchstate, operating the plurality of clutches in a fault state, wherein theunauthorized clutch state is identified by comparing the vehicle speedand the clutch position against a lookup truth table; and rows of thelookup truth table comprise lower and upper speed thresholdscorresponding to a set of unauthorized clutch positions.
 2. (canceled)3. The method of claim 1, wherein the plurality of clutches are operatedin the fault state only when the duration of the unauthorized clutchstate exceeds a fault tolerant time.
 4. The method of claim 3, whereinthe fault tolerant time is a fixed value.
 5. The method of claim 1,wherein the steps of determining the vehicle speed, determining theposition of the plurality of clutches, identifying the unauthorizedclutch state, and operating the plurality of clutches in the fault stateare implemented by the diagnostic controller distinct from the drivelinecontroller.
 6. The method of claim 5, further comprising, at thedriveline controller, while the plurality of clutches are not in theunauthorized clutch state, operating the plurality of clutches based onoperator interaction with an input device.
 7. The method of claim 1,wherein the steps of determining vehicle speed, determining the positionof the plurality of clutches, identifying the unauthorized clutch state,and operating the plurality of clutches in the fault state areimplemented by the diagnostic processing unit distinct from thedriveline processing unit, and wherein the diagnostic processing unitand the driveline processing unit are included in a vehicle controller.8. The method of claim 1, wherein operating the plurality of clutches inthe fault state includes disengaging one or more of the plurality ofclutches.
 9. The method of claim 1, wherein the plurality of clutchesare operated in the fault state by overriding commands from thedriveline controller or processing unit.
 10. A vehicle system,comprising: a transmission including a plurality of clutches selectivelyengaging and disengaging to place the transmission in one of a pluralityof discrete gear ratios; a diagnostic controller or processing unitincluding: instructions that, when executed, cause the diagnosticcontroller or processing unit to: determine vehicle speed from a vehiclespeed sensor; determine a driver pedal request; determine a position ofeach of the plurality of clutches; and identify an unauthorized clutchstate based on the clutch positions and a vehicle speed; instructionsthat, when executed, while the unauthorized clutch state persists longerthan a fault tolerant time and the driver pedal request is below athreshold, cause the diagnostic controller or processing unit to:operate the plurality of clutches in a fault state; and instruction whenexecuted, with the unauthorized clutch state and the driver pedalrequest above the threshold, cause the diagnostic controller orprocessing unit to resume operation of the plurality of clutches anddeactivate the fault state.
 11. The vehicle system of claim 10, whereinthe unauthorized clutch state is identified using a lookup truth table.12. The vehicle system of claim 11, wherein, in the lookup truth table,a single condition is used to identify the unauthorized clutch state.13. The vehicle system of claim 10, wherein the fault tolerant time isdynamic and is adjusted based on one or more vehicle operatingconditions.
 14. The vehicle system of claim 10, wherein the transmissionis an automatic transmission.
 15. The vehicle system of claim 10,wherein the transmission is a hybrid transmission.
 16. The vehiclesystem of claim 10, wherein a locking clutch is included in adifferential.
 17. A method for operation of a vehicle system,comprising: at a diagnostic controller independent from a drivelinecontroller, determining vehicle speed from a vehicle speed sensor;determining a position of a plurality of clutches in a transmission ofthe vehicle system; identifying an unauthorized clutch state bycomparing the vehicle speed and the clutch positions against a lookuptruth table; and responsive to the identification of the unauthorizedclutch state and when the unauthorized clutch state exceeds a faulttolerant time, operating the plurality of clutches in a fault state,wherein rows of the lookup truth table comprise lower and upper speedthresholds corresponding to a plurality of unauthorized clutch settings.18. (canceled)
 19. The method of claim 17, wherein operating theplurality of clutches in the fault state includes disengaging one ormore of the plurality of clutches by overriding commands from thedriveline controller to prevent torque transfer to a plurality of drivewheels from the transmission.
 20. The method of claim 17, wherein theplurality of clutches are included in a hybrid transmission.